The present invention relates to a power consumption protocol or method for selectively controlling the power consumption of a telemetry unit having a power source. The invention is of particular advantage in controlling the consumption of power from a piezoelectric power generator, for supplying power to a remote telemetry apparatus for transmitting data from a rotatable body, for example from within a pneumatic tyre.
It is known to provide a tyre monitoring apparatus for measuring the pressure within vehicle tyres. The tyre monitoring apparatus may also measure other parameters within a tyre environment, such as the local temperature of a tyre. The measured data is transmitted, for example via a radio wave link, to the cabin of the vehicle where it is electronically processed before being displayed to the vehicle driver. This enables the recipient of the transmitted data to monitor changes in the condition of the tyre, for example to reduce damage to the tyre(s) of a vehicle, or to predict tyre failure. This is of particular advantage at high vehicle speeds, when the environment within a tyre is at its most hostile and the likelihood of damage to a tyre and, indeed, injury to the occupants of the vehicle, is at its greatest.
The majority of existing tyre monitoring apparatus use a battery as the power source, which is located on or within a wheel or tyre. Such arrangements have several undesirable limitations, for example limited battery life and size or weight which can be accommodated within a tyre. This can have a further undesirable knock on effect, in that if there is a limited power source available, for example as a result of weight implications, the number and frequency of data transmissions that can be relayed for processing is compromised.